The change law about soil shear strength under freezing-thawing cycles was controversial，and calculation basis for projects were absented. In this paper，based on new sample preparation standard，by triaxial test，the representative soils in seasonal frozen region are selected as the sample，the change law about soil shear strength index under freezing-thawing cycles were studied. We define the correction coefficients of freezing- thawing cycles，on basis of soil shear strength index before freezing-thawing cycles，to present the typical soils¢ shear strength calculation formula under freezing-thawing cycles. The results show The conventional sample preparation standard shouldn¢t be applied in the freezing-thawing cycles experiments，or the discreteness of sample density will be amplified to further result in that the experimental results likely become discrete and ruleless. Under freezing-thawing cycles，the cohesion of clay，silty clay and silty sand decreased exponentially；meanwhile，the internal friction angle increased exponentially with the times increase of freezing-thawing cycles. After freezing-thawing cycles，for silty sand，the cohesion decreased about 20% and the internal friction angle increased about 10%，the freezing-thawing stability of silty sand was the best；for silty clay，the cohesion decreased about 55% and the internal friction angle increased about 20%，the freezing-thawing stability of silty clay was better；for clay，the cohesion decreased about 70% and the internal friction angle increased about 40%，the freezing-thawing stability of clay was the worst.